sj-pdf-1-asp-10.1177_00037028221077119 – Supplemental Material for Pushing the Limits of Surface-Enhanced Raman Spectroscopy (SERS) with Deep Learning: Identification of Multiple Species with Closely Related Molecular Structures

Supplemental Material, sj-pdf-1-asp-10.1177_00037028221077119 for Pushing the Limits of Surface-Enhanced Raman Spectroscopy (SERS) with Deep Learning: Identification of Multiple Species with Closely Related Molecular Structures by Alexis Lebrun, Hubert Fortin, Nicolas Fontaine, Daniel Fillion, Olivier Barbier, and Denis Boudreau in Applied Spectroscopy</p

Emission of Volatile Organic Compounds to the Atmosphere from Photochemistry in Thermokarst Ponds in Subarctic Canada

Climate warming is accelerating the thawing of permafrost, which contains almost twice as much carbon as the atmosphere, to a point where a large quantity of dissolved organic matter (DOM) is being mobilized toward surface waters, including thermokarst ponds. DOM can be partially photodegraded into volatile organic compounds (VOCs), which are little studied in Arctic environments. The main objective of this work is to identify and quantify the VOCs emitted to the gas phase by photochemistry from thermokarst water sampled in four ponds from two study sites in northern Quebec. VOC emissions were characterized by proton-transfer reaction mass spectrometry. Results show rapid photoproduction of between 35 and 59 VOCs when DOM water samples are exposed to radiation. Our results also show that the quality of DOM is a more important factor to control VOC photoproduction than the quantity of DOM. Depending on the assumptions used in upscaling our laboratory results to the field sites, calculations yield net carbon fluxes between 1.93 and 174 μmol C m–2 d–1. While these values are small compared to literature values of CO2 and CH4 fluxes from thermokarst ponds, this process represents an important flux of reactive molecules that could affect Arctic atmospheric chemistry

Theoretical Insights into Optoelectronic Properties of Non-Fullerene Acceptors for the Design of Organic Photovoltaics

Organic photovoltaics based on non-fullerene acceptors (NFAs) have gained enormous interest over the past few years. Recent fused-ring systems such as ITIC, IDT, and Y families are particularly promising for several photovoltaic devices. Since the complexity of these molecular designs has grown substantially, the development of materials with specific properties has become a laborious process. Therefore, many studies employ computational modeling, in particular density functional theory (DFT), to anticipate material electronic properties. Such approaches provide useful information about proposed organic semiconductors, such as optical absorption, frontier orbital energy levels, and molecular geometries. However, the accuracy of the common methods for recent organic semiconductors has not been explored. Thus, we herein evaluate a series of DFT functionals and Hartree–Fock (HF) theory for a collection of 14 common NFAs. Computational results are compared with physical properties from cyclic voltammetry, photoelectron spectroscopy, UV–visible absorption spectroscopy, and ellipsometry. By applying empirical corrections from linear fits, mean absolute errors between theoretical and experimental results below 0.05 eV could be achieved for the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energies as well as maximum absorption energies. Moreover, all of these experimental results for these 14 common NFAs could be useful for future device optimization

Sunlight Induces the Production of Atmospheric Volatile Organic Compounds (VOCs) from Thermokarst Ponds

Ground subsidence caused by permafrost thawing causes the formation of thermokarst ponds, where organic compounds from eroding permafrost accumulate. We photolyzed water samples from two such ponds in Northern Quebec and discovered the emission of volatile organic compounds (VOCs) using mass spectrometry. One pond near peat-covered permafrost mounds was organic-rich, while the other near sandy mounds was organic-poor. Compounds up to C10 were detected, comprising the atoms of O, N, and S. The main compounds were methanol, acetaldehyde, and acetone. Hourly VOC fluxes under actinic fluxes similar to local solar fluxes might reach up to 1.7 nmol C m–2 s–1. Unexpectedly, the fluxes of VOCs from the organic-poor pond were greater than those from the organic-rich pond. We suggest that different segregations of organics at the air/water interface may partly explain this observation. This study indicates that sunlit thermokarst ponds are a significant source of atmospheric VOCs, which may affect the environment and climate via ozone and aerosol formation. Further work is required for understanding the relationship between the pond’s organic composition and VOC emission fluxes